Wave-signal receiver, including a disabling arrangement



April 19, 1949. J, J OKRENT 2,467,564

WAVE-SIGNAL RECEIVER, INCLUDING A DISABLING ARRANGEMENT Filed Oct. 15, 1944 INVENTOR JASPER J.OKRE T A'l'l' RNEY fiatented Apr. 19, i94

UNITED STTE S Al" OFFICE WAVE-SIGNAL RECEIVER, INCLUDING A DISABLING ARRANGEMENT Application October 13, 1944, Serial No. 558,532

(01. ZED-20) Jasper J. Okrent, Grea '7 Claims.

This invention is directed to a wave-signal receiver including an arrangement for disabling the receiver in response to an abnormal variation of a predetermined operating condition of the receiver. While being subject to a variety of applications, the invention is especially suited for in-- clusion in a wave-signal transpondor system and will be particularly described in that connection.

As used throughout this specification, the term wave-signal transpondor system is intended to designate a wave-signal translating system including a receiver and a transmitter arranged to transmit a reply signal in response to a received interrogating signal, each such signal preferably comprising a pulse-modulated radiant-energy signal.

In one prior transpondor system, the receiver is of the superregenerative type and the transmitter is triggered, or set into operation, under the control of the receiver :through an amplitudeselective circuit. Optimum sensitivity of such an arrangement is obtained by adjusting the receiver gain to a compromise value between that corresponding "to maximum receiver sensitivity and that which is necessary to assure freedom from triggering the transmitter on the quiescent signal output of the receiver. This quiescent signal comprises the noise-signal output of the receiver which is obtained during intervals when no desired signal is being received. In general, the quiescent signal has a relatively low amplitude, as determined by the noise signals and other inherent disturbances of the receiver circuit, but its amplitude varies with variations of the operating potentials, tube characteristics and other factors. In order .to maintain freedom from triggering the transmitter on the quiescent signal, it is customary to embody a gain-control arrangement in the receiver. The gain-control arrangements known in the art usually comprise a signal-translating channel for translating and rectifying at least a selected portion of the quiescent signal of the receiver to derive a gain-control voltage. The gain-control voltage varies with variations in the gain characteristic of the receiver and is utilized to stabilize the receiver gain so as to maintain the amplitude of the uiescent signal output at that value required for optimum sensitivity.

While receivers of the type under consideration, stabilized by the described gain-control arrangements, are generally satisfactory, they are subject to certain operating limitations which may be undesirable in particular installations. Specifically, in the event of a failure in the gaincontrol arrangement, the gain-control voltage reaches an extreme value in the direction to increase the receiver sensitivity and gain. As a result, the amplitude of the quiescent signal output may increase sufiiciently to trigger the associated transmitter. This phenomenon is termed false firing and may be most undesirable.

Shut-down circuits have been proposed for effectively interrupting the coupling between the receiver and transmitter in case of a failure in the gain-control system so as to preclude the false firing described above. One such arrangement is shown in copending application Serial No 558,531, now abandoned, filed concurrently herewith, in the name of Jasper J. Okrent, and assigned to the same assignee as the present invention. Where the receiver is of the superregenerative type, it may frequently be more advantageous to disable the superregenerative detector itself. This not only obviates false firing of the transmitter but also eliminates radiation of the quiescent output signal of the receiver during operating intervals when the transpondor system is defective which is a desirable feature especially for military installations. However, if a shut-down circuit of the type disclosed in the aforementioned application is utilized in the manner suggested, the receiver may under certain circumstances be disabled while the gaincontrol arrangement is, in fact, functioning normally. Suppose, for example, that :the operation of the superregenerative detector is momentarily interrupted for some reason or other but that the control arrangement is in a completely opera'tive state. By interrupting the detector operation, the signal input to the gain-control arrangement falls to zero and the shut-down circuit operates to disable the receiver just as though the gain-control arrangement had failed. This operation of the shut-down circuit may be undesirable in that it prevents the receiver from being restored to normal operating conditions when the momentary interruption of its detector circuit has terminated.

The invention proposes a new type of control arrangement which is peculiarly adapted to any wave-signal receiver having a signal generator included as a necessary component thereof, such as a superregenerative receiver including a quench-signal generator. The proposed arrangement takes advantage of the fact that a monitor signal may be derived from the signal generator of the receiver and may be utilized for monitor-'- ing purposes. As applied to receivers of the type discussed above, the monitor signal controls We shut-down circuit to disable the receiver only in response to a true failure of the gain-control arrangement.

It is an object of the invention to provide an improved wave-signal receiver including an arrangement for disabling the receiver in response to an abnormal variation of an operating condition of the receiver and which avoids one or more of the above-mentioned limitations of the described arrangements. 7

It is another object of the invention to provide an improved wave-signal receiver including an arrangement for monitoring at least a portion of the receiver and for diabling the receiver in response to an abnormal variation of a predetermined operating condition of the monitored portion.

It is a specific object of the invention to provide an improved wave-signal receiver including .a. gain-stabilization arrangement and means for monitoring the gain-control arrangement to provide a cont-r01 effect effectively to disable the receiver in response to an abnormal variation of a predetermined operating condition thereof. In accordance with the invention, a wavesignal receiver including an arrangement for disabling the receiver in response to an abnormal Variation of a predetermined gain condition thereof comprises a signal-translating channel having a predetermined gain condition and means for applying to the channel for translation therethrough received signals and in the absence of received signals a quiescent signal representing inherent electrical disturbances. This means includes a signal generator associated with the signal-translating channel at least during receiving intervals for effecting the application of the signals to the channel. The receiver additionally is, provided with means for deriving from the signal generator a monitor signal and for applying the monitor signal directly to the signaltranslating channel independently of any received signal and any quiescent signal, and means responsive to at least one of these applied signals after translation through the channel for deriving an output signal having amplitude levels within a predetermined range of values for normal gain conditions of the channel and having abnormal amplitude levels outside the predetermined range in response to the substantial absence of all of the translated signals caused by an abnormal variation of the gain condition of the channel. The receiver also includes amplitude-selective means responsive primarily only to such abnormal amplitude levels of the output signal for deriving a control effect and means for utilizing this control effect effectively to disable the receiver.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 is a schematic circuit diagram of a wave-signal transponder system, embodying the present invention in a preferred form, and Fig. 2 is a graph utilized in explaining the operation of a portion of the Fig. 1 arrangement.

Referring now more particularly to Fig. 1, there is represented a wave-signal transponder system for translating pulse-modulated signals and. including an arrangement, in accordance witlithe present invention, for providing a control effect in response to an abnormal variation of a predetermined operating condition of the receiver portion thereof. For convenience of explanation, the system is illustrated as a radio beacon adapted to transmit direction-finding information to inquiring aircraft.

The beacon includes a receiver of the superregenerative type having a linear mode of operation. This receiver comprises an oscillator including a vacuum tube I!) having anode, cathode and control electrodes. A frequency-determining circuit is coupled to the anode and control electrodes of tube l0 through coupling condensers II and I2, respectively, this circuit being in the form of a transmission-line section of adjustable electrical length. The transmission-line section is provided by a pair of parallel conductors l3 and M of uniformly distributed inductance and capacitance and a short-circuiting element l5 adjustable therealong to determine the effective electrical length of the transmission-line section and the operating frequency of the oscillator in well-known manner. The cathode of tube I0 is grounded through a choke l6 and an operating bias potential is applied to the tube through additional chokes l7 and I8 from a bleeder network. The bleeder network consists of resistors l9 and 2G and a variable resistor 2|, connected across terminals B and +3 of a potential source. A source of space current is applied to tube I I! in a manner to be pointed out hereinafter.

A quench-signal generator is associated with oscillator to for supplying a periodic quench signal thereto to provide superregeneration. This signal generator comprises a vacuum tube 25 arranged in an oscillatory circuit of the Hartley type. The oscillator has a frequency-determining circuit including an inductor 26 and an adjustable condenser 21, coupled to the control electrode of tube 25 through a condenser 28 and grid resistor 29. The anode of tube 25 is effectively connected with its frequency-determining circuit by means of a condenser 30 while the cathode thereof is directly coupled to a tap on inductor 26. A source of space current, indicated +B, is applied to the anode of the tube and a quench-signal output derived from the cathode circuit is delivered to oscillator Ill through a condenser 3| and choke 11. The quench signal supplied by oscillator 25 may have a sinusoidal or other suitable wave form but has a frequency which is low with reference to the operating frequency of oscillator I 0. Also, the quench frequency is high in comparison with the pulse-repetition frequencies of interrogating signals to be received by the beacon, preferably, being so high that the quench period is equal to or less than the pulse duration of a received signal. Chokes l1 and I8 are selected to isolate the oscillations generated in the receiver circuit from the quench-signal generator and fromthe lbiasing circuit of resistors |9-2l, inclusive. A diode detector 32 is coupled to the control electrode of tube It) by way of a condenser 33. This diode provides means for deriving from the receiver an output signal having an amplitude characteristic determined by the receiver gain characteristic. A resistor 34, by-passed by a condenser ;55, and a signal-frequency choke 36 constitute the load circuit of diode 32.

The receiver portion of the radio beacon also comprises a signal-translating channel, specifically, a gain-stabilization channel having apredetermined operating condition, such-as a predetermined gain condition. This channel includes a pulse amplifier 40 of one or more stages associated with the described superregenerative detector and, therefore, associated with the signal generator 25 during intervals of wave-signal translation through a signal-frequency choke 4!. Thus, choke 4! comprises means for applying the signal output of the detector 32 to the channel including pulse amplifier All for translation therethrough. The channel under consideration further includes an automaticgain-stabilization or A. G. S. amplifier 42 of one or more stages coupled to the output circuit of pulse amplifier 40. The A. G. S. amplifier preferably includes selector circuits arranged to select the quenchfrequency component of the detected signal output of the receiver for utilization in stabilizing the receiver gain.

To facilitate monitoring the described signaltranslating channel in order to ascertain its operating state or condition, the receiver has means for deriving from the quench-signal generator a monitor signal and for applying the monitor signal to the channel for translation therethrough at least in the absence of received wave signals. To this end, the signal-translating channel is directly coupled to the output circuit of quench-oscillator 25 through a T-net- Work of impedance 43, Ml and :35. This network is selected to supply to the gain-stabilization channel a monitor signal of low intensity as compared to the receiver detected signal output, but preferably with substantially the same phase as the quench-frequency component of that detected wave-signal output. In the illustrated arrangement the desired phase relation of the signals applied to the channel is accomplished by using resistors in the Tnetwork. However, T- network 43% may, if desired, be augmented with a suitable phase-shifting circuit for securing any particular phase relation.

There is coupled to the output circuit of A. G. S. amplifier 42 means dependent upon the translation of signals through the described signaltranslating channel for deriving therefrom an output signal having amplitude levels determined by the gain characteristic of the receiver and within a predetermined range of values for normal operating conditions of the receiver but having abnormal amplitude levels outside this range of values in response to an abnormal variation of the operating conditions of the receiver or of the gain condition of the gain-stabilization channel. This means comprises an A. G. S. rectifier, including a diode rectifier t6, coupled to the output circuit of A. G. S, amplifier 342 by a coupling condenser 41. The load circuit of diode it is provided by a resistor 38, a filter resistor 39 and a by-pass condenser 49. The rectifier circuit has a fast-charging time constant and a slow-discharge time constant so as to peak-rectify the applied signal output of amplifier Q2.

The signal output of the rectifier, as obtained across its load resistor 48, is applied with positlve polarity to the input circuit of an amplifier including a vacuum tube 59. A bias potential, derived from a bleeder network provided by a resistor 5| and a voltage divider 52 connected in circuit with a suitable potential source, indicated B, is likewise applied to the input circuit of tube 50 through resistor 48 and an adjustable tap on the voltage divider. The magnitude of this bias potential is selected of such value that, in the absence of a control signal from A. G. S. rectifier 46, tube 50 is biased substantially to anode-current cutofi. A source of space current +B- is coupled to the anode of tube 50. A unidirectional potential, having a magnitude determined by the conductive state of tube 50, is derived from the anode-cathode circuit thereof and is utilized as a source ofspace current for re-- ceiver tube It. To this end, the anodes of tubes 56 and it are coupled through a resistor 53 and a filter provided by series inductors 54 and 55 and shunt condensers 56 and 5?. Tube 5%} constitutes means for utilizing the output signal of the gainstabilizati'on channel to control the gain characteristic of the receiver through an adjustment of the anode-cathode excitation potential of tube it.

The receiver is also provided with an amplitudeselective means responsive to abnormal amplitude levels of the output signal of the A. G. S. rectifier 36 for deriving a control effect. This last-named means comprises an electron-discharge device, specifically a triode amplifier including a vacuum tube 5 having its anode-cathode circuit connected in shunt relation to resistor 69 of the biasing circuit of receiver tube Ill. Tube 60 is normally biased to anode-current cutoff by a suitable bias potential B coupled to the input circuit thereof through a variable resistor 6|, A resistor 62 couples the input circuit of tube 60 to the output circuit of amplifier 5% in order that tube 595 may be rendered conductive in response to abnormal amplitude levels of the output signal of the A. G. S. rectifier 36 for deriving a control effect. This control effect is produced in the biasing circuit of elements l9--2l and is utilized so to adjust the operating bias of oscillator H] as efiectively to disable the receiver portion of the beacon.

The transmitter portion of the radio beacon comprises a balanced ultra-hig-h-frequency oscillation generator it, forming the subject matter of copending application Serial No. 527,753, filed March 23, 1944, now Patent No. 2,431,762 issued December 2, 1947, in the name of Leonard R. Malling and assigned to the same assignee as the present invention. This generator operates at substantially the same frequency as the re ceiver and includes a pair of vacuum tubes 'H "52. A first balanced transmission line of the feed-through type, comp-rising a pair of open conductors l3 and it is directly coupled. to the anode electrodes of tubes 1! and 12. Adjustable tuning elements 15 and 16 are included in the line and constitute therewith a frequency-adjusting circuit for tuning the generator. A second balanced transmission line of the feed-through type, provided by a pair of conductors Ti and I8, is coupled to the control electrodes of tubes TI and '52 and extends therefrom in the same direction as the first-described line. A grid resistor 19 is coupled to the control electrodes of the tubes through a signal-frequency choke Bil and transmission line ll, '68. A detailed description of this generator is included in the above-mentioned copending application.

Generator i6 is controlled by the receiver portion of the beacon through a connection 85, extending between the output circuit of pulse amplifier 49 and the input circuit of a unit 86. Unit 86 may be of conventional design and construction and includes a multivibrator adapted to be keyed into operation by an amplitude-selective trigger circuit to generate a single pulse of unidirectional potential, preferably, having a rectangular wave form and a controllable pulse duration. The output circuit of unit 86 is coupled through a pulse amplifier 81, a pulse transformer waneMiguel-frequency choke 89 "to the anode= cathode circuit of generator 10.

4 single antenna-ground system 90, utilized foi' 'both receiving and transmitting, is magnetically 'coupled to the frequency-determining circuits of'oscillators l and of the receiver and transmitter portions, respectively, b'y*means of an iiiductortl. Inductor 9| is so positioned'with' respect 'to the frequency-determining circuits of oscillators l0 and 10 as to have a substantial magnetic coupling therewith, indicated by bracket's' M and M, for any adjustments of shortcircuiting-elements l5 and I5, 16.

Neglecting for a moment the direct coupling between quench-signal generator and-pulse ani'plifier' 40 and the function of the control circuit-including vacuum tube 60, the described arrangement constitutes a conventional radio beaeen -theoperation of which is well underst'ccii'by those skilled in the art so that a detailed description thereofis unnecessary herein. Briefly'i -during quiescent operating conditions when no slgn'al is intercepted-by antenna system 90, oscillations are periodically produced by oscillator' 'lllpf the receiver circuit under the control oifth'e quen'ch voltage supplied by'oscillator 25. These'oscillations are initiated by-the low-amplitud=noise signalsand similar disturbances inherntin the receiver circuit and have a correspondingly small amplitude value. The generated oscillations aredetected by detector 32, producing'across resistor 34 the low-amplitude quiescent 'signal output discussed above. This quiescent signal output 'is' applied to pulse amplifierll'for translation through-the described gain-stabilization channel of the receiver. Thus, this channel is effective in the absence of received wave signals to translate a quiescent signal representing-inherentdisturbances withinthe receiver. Aiten'amplification in pulse amplifier 40, the quench-frequency component of the quiescent si'g'na'l is selected and further amplified in A. G. S. amplifier 42 and applied to rectifier 46 for rectification. The resulting output signal of the rectifier, obtainedacross its load resistor 48, comprises -'a substantially unidirectional potential.

Th'output signal of the A. G. S. rectifier is applied with positive polarity to the input circuit of 'vacuum tube 50 and in conjunction with the biasing" arrangements thereof determines the conductivity of tub 50 and, consequently, the magnitude of the unidirectional potential obtained therefrom and applied to the anodecath'ode' circuit of oscillator in. The circuit parameters and operating potentials of the gainco'ritrolarrangement and amplifier 50 are so selctedthatunder normal conditions of operatlon the excitation potential thus applied to oscillator H] has that value which is required to' esta-blish optimum sensitivity of the-receiver circuit. Any variation in the gain of the receiver manifests itself in an amplitude variation-ofits' quiescent signal output which, in turn, produces like'variations in the magnitude of the output signal ofA; G. S. rectifier 46. Should the magnitude of this signal output increase, the con-' ductivity of tube 50 is increased thereby reduclng' the "anode-cathode excitation potential of tube I 0' to restore the desired gain" condition of-the receiver. On the other hand, a decrease in the outputsignal of rectifier 46, indicating a loss ofga'in in thereceiver, increases theanodecathode potential-of receiver 10 as required to stabilize" the receiver gai'n' and sensitivity. a.

'Ifi -quiescent-signal "output of the receiver trigger circuit of unit 86 and trigger transmitter' Let it be assumed; now,-that an aircraft de sirlng direction-finding information 'from the beacon transmits thereto a pulse-modulated'interrogating signal.

In general, this signal has ahigh intensity with reference-to the noise-signal of the-receiver circuit so that oscillations gen-- erated in the receiver in any quench'cycle' occurring within the duration of a received pulse have 1 a relatively high amplitude. During intervals which intervene between pulsesof the received signal, the output signal of detector n comprises the low-amplitude quiescent signal mentioned above. The resulting output signal of the receiver, including both the high-amplitude and low-amplitude signal components, is supplied topulse amplifier 40 for translation'through thegain-stabilization channel to maintain the (le sired gain of the receiver in the manner indi cated above. Inthe usual installation, the pulserepetition frequencies of received-interrogating signals are sufiiciently low that the high-amplitude components of the receiver output signal, representing the pulse modulation of a received signal, have no appreciable adverseeifect on the described operation of the gain-control arrangement.

This outputsignal of the receiver derived in response to a received interrogating signal is like- 1 wise applied through pulse amplifierlnvto unit 86. The first high-amplitude signal component. derived from eachreceived pulse of the interrogating signal causes the trigger "circuit of unit 86 to excite its associated multivibrators-and generate a pulse of unidirectional potential for; application through units 81 and88to oscillation" generator 10. Oscillations are continuously generated in unit 10 for'the duration of each applied pulse of unidirectional potential and are transmitted by antenna system 90. Therefore, in response to a received interrogating signal, the' beacon transmits a pulse-modulated replyv signal having the same pulse-repetition frequency as the received signal and having a pulseduration determined by the adjustments'of the multivibrator included in unit 86. The inquiring aircraft is thus able to obtain the desired bearing indication or other direction-finding information from such transmitted reply signals.

In considering the effect of the monitor signal applied from quench-signal generator 25 to the gain stabilization arrangement and the operation of the control circuit including vacuum tube 60, reference'is made to the curve of Fig. 2. This curve' illustrates the variations in the anodecathode potential of tube [0 in response to ampli tu'de variations of the signal output of A. G. S. diod'e lfi. During intervals of normal operation when the entire receiver arrangement is functioning properly, the signalinput to diode from A. G. S. amplifier 42 has two components: (1) the quench-frequency component of the detected signal output of the detector 32 and (2) the monitor signal obtained from quench-signal generator 25 through resistors, and 45. For such conditions, the outputsignal of A. G: S. detector 46 has an amplitude level'within a given range of'values represented by dimenslonline at in -Fig 2. In response to this output signal the anode-cathode 1 potential of receiver tube IO- 1's controlled by amplifier 50, in the manner indicated above, to have amplitude levels within a normal range of values, designated by dimension line y in Fig. 2. Ranges :1: and y are not coextensive for a reason to be pointed out presently. The blocking bias applied to the input circuit of tube 6!) is selected of such value that the anodecathode voltage of receiver tube it must reach a value indicated by ordinate line b to overcome this bias and render tube 69 conductive. Therefore, during normal operating conditions, tube 69 remains blocked and the receiver is conditioned for operation.

Assume, now, that the circuit of receiver tube H3 is interrupted momentarily but that the operation of the gain-stabilization arrangement is unimpaired. Such conditions are frequently realized in transpondor arrangements Where it is necessary to suppress the transpondor opera tion for brief intervals as, for example, when other equipment in a nearby installation having closely associated operating frequencies is to be utilized. Such momentary interruptions may be accomplished through suitable switching circuits which have been omitted from the drawing for the purpose of simplicity. While receiver tube may be disabled during these intervals, quenchsignal generator 25 continues to supply a monitor signal directly to pulse amplifier Mi through resistor network d3, 44, 35. Since the gain-control arrangement has been assumed to be functioning properly, an output signal of reduced amplitude, indicated by abscissa dimension 0-0 and corresponding to a limiting value of the range of values :0 is obtained from the circuit of rectifier d6. establishing the anode-cathode potential of tube ill at a value indicated by ordinate line 0. This voltage level is still below that required to energize control tube 6i and consequently at the termination of the receiver suppression interval, normal operating conditions are re-established throughout.

However, in the event of a failure of the gaincontrol arrangement, whether receiver tube i0 is disabled or not, the output signal of rectifier 46 has an abnormal amplitude level outside of the range designated a. Specifically, the amplitude level of this signal output is reduced to zero. Tube 56 is then driven substantially to anodecur'rent cutofi by its biasing circuit including voltage divider i and the anode-cathode potential of receiver tube It rises to its maximum value, indicated by ordinate line d. With this abnormally high anode-cathode voltage applied to tube Ii], the amplitude of its quiescent signal output may reach a sufficient level to energize the trigger circuit or" unit 85 and initiate false firing of transmitter it. This undesired result, however, is precluded by the operation of vacuum tube 69 which is rendered conductive in response to the rise of anode potential of tube 553 following such an abnormal amplitude level of the output signal of the gain-control arrangement. When tube 60 is conductive, the bias potential applied from bleeder network !92l to the control electrode of tube it has sufiicient magnitude to hold the receiver blocked. In this manner the amplitude of the quiescent signal output is reduced substantially to zero value, thereby obviating false firing of the transmitter which may otherwise occur.

From the foregoing description it will be clear that the range or represents the range of values of the signal output of rectifier M5 for all operating conditions in which the gain-stabilization arrangement exhibits its normal operating char-- acteristics. Inasmuch as the gain-stabilization arrangement may function properly even though receiver tube it is temporarily disabled, this range of values so is greater than the range y, the allowable range of anode potential applied to tube l0 during intervals in which both the receiver tube it and the gain-stabilization arrangement are operating normally. It also will be apparent from the above description that the monitor signal prevents permanent blocking of the receiver by the control circuit of tube Bil as a result of conditions arising during the warm-up period after the receiver is first turned on. If the monitor signal were not used, tube 63 might warm up faster than all of tubes 25, it, fail and all of the tubes of units ill and t2 and would then operate permanently to bias oiI" the superregenerator ill. With the monitor signal, however, normal operating conditions are established as soon as the oscillator 25 causes a monitor signal to be effectiveat the amplifier Eli and this is true even in the event that the superregenerator it may have been temporarily biased on by the tube so due to some warm-up condition.

While the control circuit including tube 60 may be used to interrupt the coupling between the receiver and transmitter portions of the beacon, as by biasing one of units 86 or 87 to cutoff, it is preferred that the control effect be applied to receiver tube it as described. This utilization of control effect is particularly advantageous in that it prevents radiation of the quiescent signal output of the receiver during intervals of abnormal operating conditions. Although the same result may be obtained by interposing a suitable stage or radio-frequency amplification between the superregenerative detector and the antenna system, it is more desirable to omit such stages of amplification in order to obtain a maximum signal-to-noise ratio.

It will be understood that other methods of applying the quench-signal voltage to the superregenerative detector may be employed. For example, the quench voltage may be applied to the anode-cathode circuit of tube it. Likewise, in establishing a gain control of the receiver, the gain-stabilization channel may be used to vary the amplitude of the applied quench signal.

t will be further understood that the described invention is not limited in application to a receiver of the superregenerative type. Also, the invention is not restricted to the monitoring of a gain-control arrangement of a Wave-signal receiver. If desired, the principal signal-translating channel of the receiver or particular components thereof may be monitored in the manner described to derive a control effect in response to an abnormal variation of a predetermined operating condition.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A wave-signal receiver including an arrangement for disabling said receiver in response to-an abnormal variation of a predetermined gaincondition thereof, comprising: a signal-translating channel having a predetermined gain condition;

means for applying to said channel for translation therethrough received signals and in the $11 rabsence -of receivedzsign-als 'a' quiescent sig'nalzreprre'senting inherent electrical disturbances, said meansi including t a signal generator. associated with said channel at least during receivinginterr vals for :efi'ecting said application of said signals :t'ousaid channel; means for deriving from: said isignalzgenerator a monitor signal and for applyrlnghs'aid'monitor signal directly to said channel independently of any received signal and any --iqui'escentsignal;- means responsive to at least "one of said applied signals after translation through said channel for deriving an output signal h'avlng 'amplitude levels within a predetermined range of values-for normal gain conditions of said channel and having-abnormal amplitude levels outside ofsaidrange in response to-the substantial absence of all of said translated signals caused "byan abnormal variation of the gain condition *of said' channel; amplitude-selective meansred control'eifect effectively todisablesaid receiver.

4. .A;-wave-:signalreceiver of the superregenerative: type including :an arrangementfor. disabling said receiver in response to an abnormal'avariaction of apredeterminedn'gain condition thereof,

comprising: a' signal-translating channel having ;a predetermined gain condition; a superregenerative: detector :for detecting =received wave signals zandfor applying toxsaid'channel fortranslation -th'erethrough' the'detectedsignals andin the ab- .a i primarily only to said abnormal ampm 2 rsence of 'rec'eived' 'signals:a'quiescent signal repre- 'tude levels of said output signal for deriving a --control-efiect;-and meansfor utilizing said control flecfiefiectively to disablesaid receiver.

2. A wave-signal receiver of the superregeneralsenting' "inherent" electrical disturbances; said nuperregenerative 'fdetector having a quench- .sign'al :generator associated therewith for eifecting -saidzapplication to said channel of said signals;

tive t pe including an arrangement for disabling t'm'eansfor derivingjrom saidquench-slgnal "saidreceiver in response to an abnonmal varia- *tion of a; predetermined gain condition thereof, comprising: a signal-translating channel having -a predetermined' gain condition; means for ap icrator a monitorzsignaluand for: continuously ap- --plying saidtmonitorxsignal directly to said channel with substantially the same phase asthe quench- --frequency component of said" detected wave sigiplymgu to Said charm 81 for translation there? nalszbut'independently of any-received'signal'and -throughreceivedsignals and inthe absence of deceived-signals a quiescent signal representing "inherent electrical disturbances, said means incl'uding a quench-signal generator associated with s'aid channel atleast'during'receiving interv als' for effecting said application of said signals to-said channel; means for deriving from said qu'ench signalgenerator a 'monitor signal-and for applying said'monitor signal directly to said channel independently of any received signal and lanyquiesc'ent signal; means responsive to at least -one kof saidapplied signals after translation "through-said channel for deriving an -output sigslnalflhaving amplitude 'levels Within a'--predeter- 5 :F-min'e'drange of values for normal gain conditions c'ofi said channel and-having abnormal amplitude i-levelscoutsidecs'aid range in response to 'thesubstantialvlabsence of all of said translated signals ncaused'lby an abnormal variation of the gain condition oflsaid channelamplitude-selective 'means izresponsiveprimarily only to said abnormal amplirtuderlevels of'said output signal for deriving a --control.-eifect; -and=means for utilizingsaid control efiectrefiectively to disable said receiver.

3'. A'waveesignal receiverincluding anarrangeziment 'fordisabling saidreceiver in response to oamabnormalr variation of a predetermined gain conditionil thereof, comprising: a 1 signal-translating channel having a predetermined gainconedition; a detector for detecting received wave siganalsfandzfor applying to'said channel fortranslatttionatherethrough the detected signals and in the labsence 'ohreceived signals a quiescent signal Hrepresenting inherent electrical disturbances, said iidetectorehaving a signal generator associated there'with'iofiefiecting said application to said channel of s'aid signals -means for deriving from said signal generator a monitor signal and for atsiplying s'aid'monitor signal directly to said chan- -nel independently of any received signal and any quiescen't sig'nal;- means responsive to'at least one 0f "s'aidappliedsignals after translation through said channelfor'deriving an output signal hav- -ing==amplitude= levels Within a predetermined Iany quiescent signalymeans responsive to at least (one of said applied signals after translation -through saidchannel for deriving an output signal having amplitude levels within a prede- -termined range of values for normal'gain conditions of said-channel and having abnormal ampli- 'tude le'vels outside-said range in response to the substantial absence 'of'all of said translated signals caused'by ar'rabnormal variation of the gain n dillcondition 'of" said channel; amplitude-selective m'eans responsive primarily only to said abnormal amplitude levels of said output signal'ior deriving "a: control efifect; and means for utilizing said control*eflfecteffectively to disable said receiver.

' 5. Awave-signal receiver 01' the superregenerative' type'including'an arrangement for disabling "said receiver in response to an abnormal .varla- #tion of a-predetermined gain condition thereof, "comprising: a. signal-translating channel having "a predetermined gain condition; a superregenerativedetector 'for' detecting received wave signals -.andfor;applyi ng to said channelfortranslation ther'ethrough the detected signals andin the absence ofreceived signals a quiescent signal rep- "resenting inherent electrical disturbances, said supenffigenerative detecton having a. quench- -signal generator associated therewith for effectinjgsaid application to said channel of said sig- 'nals; means'for derivingfrom said quench-signal generator a monitor signal having a low intensity as; compared with said detected wave slg- "nals and for continuously applying said monitor -signal directly tosaid channel with substantially the same; phase as, the quench-frequency com- 55 ponent of said detected wavesignalsnbut. independently of any received signal andany quiescent signals; means responsive to at least, onelof said a plied signalshaiter translation through said channel for derivinguanr output,signal having "amplitude levels within a predetermined range cf values .for normal, gain. lconditions of said channel and, having, abnormal ,.ampli.tude "levelsh outside saicLrange in response ,to vthasubstantiaL absence of all totrsaidt translated signals "caused1by an abnormal r variation. ,ot, .the zaln 13 condition of said .channel; amplitude-selective means responsive primarily only to said abnormal amplitude levels of said output signal for deriving a control efiect; and means for utilizing said control effect effectively to disable said receiver.

6. A wave-signal receiver including an arrangement for disabling said receiver in response to an abnormal variation of a predetermined gain condition thereof, comprising: a signal-translating channel having a predetermined gain condition; means for applying to said channel for translation therethrough received signals and in the absence of received signals a quiescent signal representing inherent electrical disturbances, said means including a signal generator associated with said channel at least during receiving intervals for effecting said application of said signals to said channel; means for deriving from said signal generator a monitor signal and for applying said monitor signal directly to said channel independently of any received signal and any quiescent signal; means responsive to at least one of said applied signals after translation through said channel for deriving an output signal having amplitude levels within a predetermined range of values for normal gain conditions of said channel and having abnormal amplitude levels outside said range in response to the substantial absence of all of said translated signals caused by an abnormal variation of the gain condition of said channel; an electron-discharge device biased substantially to anode-current cutoiT for normal gain conditions of said channel but responsive to said abnormal amplitude levels of said output signal for deriving a control effeet; and means for utilizing said control effect effectively to disable said receiver.

7. A wave-signal receiver including an arrangement for disabling said receiver in response to an abnormal variation of a predetermined gain condition thereof, comprising: a gain stabilization channel for said receiver having a predetermined gain condition; means for applying to said channel for translation therethrough received signals and in the absence of received signals a quiescent signal representing inherent electrical disturbances, said means including a signal generator associated with said channel at least during receiving intervals for effecting said application of said signals to said channel; means for deriving from said signal generator a monitor signal and for applying said monitor signal directly to said channel independently of any received signal and any quiescent signal; means responsive to at least one of said applied signals after translation through said channel for deriving an output signal having amplitude levels determined by the gain characteristic of said receiver and within a predetermined range of values for normal gain conditions but having abnormal amplitude levels outside said range in response to the substantial absence of all of said translated signals caused by an abnormal variation of the gain condition of said channel; means for utilizing said output signal to stabilize said gain characteristic of said receiver; amplitude-selective means responsive primarily only to said abnormal amplitude levels of said output signal for deriving a control effect; and means for utilizing said control efiect effectively to disable said receiver.

JASPER J. OKRENT.

REFERENCES CITED The following references are of record in the 1c of this patent:

UNITED STATES PATENTS Numb-er Name Date 2,060,969 Beers Nov. 1'7, 1936 2,101,549 Lamb Dec. 7, 193'? 2,224,224 Hallam, Jr. J Dec. 10, 1940 2,252,811 Lowell Aug. 19, 1941 2,261,800 Freeman Nov. 4, 1941 2,264,018 Case NOV. 25, 1941 2,264,019 Case Nov. 25, 1941 2,282,834 Thomas May 12, 1942 2,300,081 White Oct. 27, 1942 2,362,958 Sandretto NOV. 14, 1944 2,414,992 Wheeler Jan. 28, 1947 

